The purpose of this proposal is to gain new insights into several biochemical and transport properties of cerebral endothelium in vitro under normal conditions and following co-culture with other brain cell types. All experiments will be performed utilizing cells derived from mouse cerebromicrovasculature. Specifically, we propose to 1) examine the cytochemical localization of several hydrolytic enzymes in cerebral endothelium in vitro utilizing an in vitro blood brain barrier model and determine the influence of glial cells on the localization of these hydrolytic enzymes on cerebral endothelial membranes, 2) examine the transport of water across cerebral endothelial membranes and the effect of various sulfhydryl-reactive agents on permeability of cerebral endothelial cells to water, 3) examine the effect of cortiscosteroids on the transport of water across cerebral endothelial cell membranes, and 4) examine the effect of corticosteroids on anionic charge distribution oni cerebral endothelial cell membranes. The information obtained from these studies should extend our understanding of the normal function of the blood-brain barrier. It should provide new information on the movement of water across the blood-brain barrier, and finally, it should provide insight into the mechanism of corticosteroid control of brain edema.